My bf and I have been together for 4 years this May. We have two kids together a 2 yr old and at the time a 7 month old. Well we were living with my dad due to finances and my dear SISTER decided to move in as well. She had just left her husband of 6 yrs and have 3 kids together well at least 2 of them are his not sure bout the 3rd. Anyways once she moved in my bf started sleeping in the living room instead of in our room. I went down stairs almost every night to make a bottle..for our youngest. I never noticed anything out of the ordinary until one night. I went down and she was in the living room too. I started getting suspicious. I would ask him as nice as I could to grab something for our youngest or make a bottle while I was changing her. And got snapped at instantly. But if my whore sister asked him to do something no matter what it was he would do it. || After about a month of this I told my dad my suspicions he said it was just jealousy. I knew he was wrong then on the 2nd of July I finally was told the truth. I pulled my dad aside and showed him messages between my bf and skunk of a sister. Saying they loved each other and how wonderful their sex was. I called my bf into the room and he told me he did indeed sleep with her. Not once but multiple times. Luckily for her she had left that morning and we haven’t seen her since. I want nothing to do with her and if I ever catch him talking to her it will be over for good. As of now we are trying to work things out and are living in our own place now.